With growing concerns and pressures to develop products out of renewable resources, various efforts have been directed at developing useable products from agricultural crops. The majority of these efforts have been directed at producing replacements for petrochemical-based plastics and fuels as well as wood-based panels, for example. Furthermore, with growing concerns and pressures to find alternative uses for waste matter, various efforts have been directed at developing useable products from recycled newsprint and other paper stocks. The majority of these efforts have been directed at producing building insulation materials, fiberboard, particle board, and the like.
Insulation materials prepared from dry, shredded cellulosic materials or multiple layers of newspaper are described in U.S. Pat. Nos. 4,184,311 (Rood) and 4,300,322 (Clark), and Australian Application Serial No. 36603/84 (Hartlett et al.). Stable blocks formed of shredded newspaper and 0.5-3% of a ligninsulfonate binder are described in U.S. Pat. No. 4,148,952 (Nelson et al.). These blocks are used to consolidate waste paper to facilitate handling and transport to locations where the blocks are shredded.
Numerous processes are known for producing structural building materials, e.g., fiberboard, panel board, particle board, from waste paper. For example, U.S. Pat. No. 4,111,730 (Balatinecz) discloses paper flake board prepared from shredded waste paper, e.g., flakes of about 0.5-2 inches by 1-6 inches, and a synthetic petrochemical-based thermosetting resin, e.g., urea-formaldehyde or phenol-formaldehyde resin. The resin is used in an amount to provide 6-15% resin solids. The moisture content of the paper flakes during blending with the resin is maintained at less than 12%. To enhance the surface quality of the resulting paper flake board and to enhance strength and stiffness, a mixture of wood flour or cellulosic matter and a formaldehyde-containing resin is coated on the surface.
U.S. Pat. No. 5,011,741 (Hoffman) discloses a multiple ply paper product, e.g., linerboard, produced from layers of Kraft pulp, i.e., pulped wood chips, and pulped newsprint, i.e., newsprint subjected to chemical dispersants used in conventional pulping processes. The pulped newsprint is substantially free of fines and fibers having a length less than 50 microns. It is impregnated with cooked cationic starch to enhance internal strength and bonding between the layers.
U.S. Pat. Nos. 4,994,148 (Shetka) and 5,064,504 (Shetka) also disclose methods for creating molded structural blocks from a newsprint slurry which is formed in a screen wall molding chamber of a press. The newsprint or other cellulosic product is combined with a sufficient amount of water, e.g., a 50:50 mixture, to pulp the paper into a flowable form. A plaster, cement, or latex binder can also be added to the aqueous pulp slurry. The resultant slurry is then poured into the molding chamber. Curing of the blocks is effected through air drying.
U.S. Pat. No. 3,718,536 (Downs et al.) discloses a composite board formed from a mass of shredded paper containing a thermoplastic polymer such as polyethylene, polypropylene, polyvinyl chloride, and the like. The composite board is made of individual pieces, i.e., sheets or shreds, of paper, arranged in an overlying and overlapping configuration, which is distinguished from composite boards made from fibrous materials prepared by wet or dry processes. In the process, the paper pieces are coated with the thermoplastic polymer, which binds the pieces together. Thus, cross-sections of the composite board reveal lamination of paper plies surface-bonded, i.e., contact-bonded, together by the thermoplastic polymer. Such materials containing thermoplastic polymers are unuseable in building products, however, because of fire regulations. This is because thermoplastic materials soften upon exposure to elevated temperatures and thereby lose their structural integrity.
All previously known panel materials containing cellulosic materials from waste paper, paper products, or pulp waste and/or agricultural products, unless separately laminated with a decorative finish laminate, have uniformly demonstrated undesirable properties. For example, they generally possess dull grey or matte grey colors without any distinctive or aesthetically appealing patterns. Furthermore, they generally lack the strength, stiffness, hardness, and durability of structural grade building materials. Also, they are generally too porous for many applications.
The lack of materials containing renewable natural resources with such desirable characteristics is believed due to a variety of factors, including, for example: (1) the lack of processing means for repeatedly producing an aesthetically pleasing texture and coloration of the finished material; (2) the lack of processing means for repeatedly producing cellulose-based material having the strength and stiffness of structural grade materials; (3) shredding and repulping of waste paper reduces the length of the cellulose fibers that can compromise the tear and shear strength of the finished material; (4) costly de-inking and bleaching of the cellulosic material, which reduces the competitiveness of the material; and (5) the potential presence of undesired contaminants in the waste paper stock that can deleteriously effect surface finish, bonding, rigidity, and structural integrity of the product.